Valve practical knowledge, you know? Valve knowledge: pilot type safety valve installation requirements and working principle

Valve practical knowledge, you know? Valve knowledge: pilot type safety valve installation requirements and working principle

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1, the basic parameters of the valve: nominal pressure PN, nominal diameter DN2, the basic function of the valve: truncated through the medium, adjust the flow, change the flow direction 3, the main ways of connecting the valve are: flange, thread, welding, clamping 4, the pressure of the valve – temperature grade: Under different materials and different working temperatures, non-impact working pressure is different. 5. There are two main systems for pipe flange size: European system and American system. The connection sizes of the tube flanges of the two systems are completely different and cannot be matched; Appropriate to distinguish by stress level: European system

Valve foundation

1, the basic parameters of the valve are: nominal pressure PN, nominal diameter DN

2, the basic function of the valve: truncated through the medium, adjust the flow, change the flow direction

3, the main ways of valve connection are: flange, thread, welding, clamping

4, valve pressure – temperature grade said: different materials, different working temperature, relatively large non-impact working pressure is different

5, tube flange size mainly has two systems: European system and American system.

The connection sizes of the tube flanges of the two systems are completely different and cannot be matched;

To distinguish appropriate by pressure level:

The European system is PN0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.3, 10.0, 16.0, 25.0, 32.0, 40.0MPa;

The American system is PN1.0(CIass75), 2.0(CIass150), 5.0(CIass300), 11.0(CIass600), 15.0(CIass900), 26.0(CIass1500), 42.0(CIass2500)MPa.

The main types of pipe flanges are: integral (IF), plate flat welding (PL), neck flat welding (SO), neck butt welding (WN), socket welding (SW), screw (Th), butt welding ring loose sleeve (PJ/SE)/(LF/SE), flat welding ring loose sleeve (PJ/RJ) and flange cover (BL), etc.

Flange sealing surface types mainly include: full plane (FF), surface (RF), concave (FM) convex (M) surface, tenon (T) groove (G) surface, ring connecting surface (RJ), etc.

Common (universal) valve

1, the valve type code Z, J, L, Q, D, G, X, H, A, Y and S respectively represent: gate valve, globe valve, throttle valve, ball valve, butterfly valve, diaphragm valve, plug valve, check valve, safety valve, pressure reducing valve, trap valve

2, the valve connection type code 1, 2, 4, 6, 7 respectively said: 1 – internal thread, 2 – external thread, 4 – flange, 6 – welding, 7 – clamp

3, the valve transmission mode code 9, 6, 3 respectively said: 9 – electric, 6 – pneumatic, 3 – turbo worm

4, the valve body material code Z, K, Q, T, C, P, R, V respectively said: gray cast iron, malleable iron, ductile iron, copper and alloy, carbon steel, chromium nickel stainless steel, chromium nickel molybdenum stainless steel, chromium molybdenum vanadium steel

5, the valve seat seal or lining code R, T, X, S, N, F, H, Y, J, M, W respectively said: austenitic stainless steel, copper alloy, rubber, plastic, nylon plastic, fluorine plastic, Cr stainless steel, hard alloy, lining rubber, monel alloy, valve body material

6, the cast iron valve body is not suitable for the occasion:

1) Water vapor or wet gas with much water content;

2) Flammable and explosive fluid;

3) The ambient temperature is lower than -20℃;

4) Compressed gas

Control valve

1. The control valve is composed of the valve body and the executing mechanism and its accessories.

2, pneumatic film actuator has two forms of positive action and reaction; With the increase of signal pressure, the downward movement of the push rod is positive, whereas the upward movement of the push rod is negative. Usually the pressure of receiving scale signal is 20~100KPa; With the positioner, the higher pressure is 250KPa. There are six basic strokes (mm) : 10; 16. 25. 40; 60; 100.

3, compared with the pneumatic actuator electric actuator, what are the characteristics of several output forms /p>

The driving source is simple and convenient, with large thrust, torque and stiffness. But the structure is complex and the reliability is poor. In small and medium size more expensive than pneumatic. Often used in no air source or do not need strict explosion-proof, flameproof occasions.

Angular stroke, straight stroke, and multi – turn three output forms.

4, longitudinal single seat control valve has any characteristics used in what occasions /p>

1) Discharge is small, because only one spool is easy to ensure sealing. Scale discharge of 0.01kV, further design can be used as a blocking valve.

2) The allowable pressure difference is small, because of the unbalanced force pushing force. DN100 valve △P* is 120KPa.

3) Low smooth flow ability. The KV* of DN100 is 120. Should be used in small leakage, pressure difference is not large occasions.

5, longitudinal double seat regulating valve has any characteristics used in what occasions /p>

1) The allowable pressure difference is large, because it can offset a lot of unbalanced force. The valve △P of DN100 is 280KPa.

2) Good smooth flow ability. DN100 has a KV of 160.

3) The leakage is large, because the two spool can not be sealed at the same time. The scale discharge is 0.1%KV, which is 10 times of the single-seat valve.

Mainly used in high pressure difference, leakage requirements are not strict occasions.

6, sleeve regulating valve has any main advantages /p>

Both single and double seat valve advantages. There are mainly:

1) Peace is good. Because the valve plug throttling replaces the valve core seat throttling, and the valve plug is provided with a balance hole can reduce the unbalanced force of the medium acting on the valve plug. At the same time, the guide surface between the sleeve and the valve plug is large, and the unbalance force is small, so it is not easy to cause the vibration of the valve core.

2) Strong interchangeability and versatility. As long as the sleeve is replaced, different flow coefficients and different flow characteristics can be obtained.

3) Large differential pressure and small thermal expansion effect. The balance principle of the sleeve valve with a balance hole is the same as that of the two-seat valve, so the allowable pressure difference is large. And because the sleeve and valve plug are made of the same material, the expansion caused by temperature change is basically the same.

4) The throttling window provided by the sleeve has two kinds: opening big mouth and punching small hole (jet type). The latter has noise reduction, reduce the excitation, further improvement is a special low noise valve.

Suitable for large pressure difference before and after the valve, low noise requirements.

7, in addition to single, double seat valve and sleeve valve, which have adjustment function of the valve /p>

Diaphragm valve, butterfly valve, O-type ball valve (mainly plugging), V-type ball valve (adjustment ratio, shear action), eccentric rotary valve.

8, what is the adjustable ratio of the regulating valve R, the ideal adjustable ratio, the actual adjustable ratio /p>

Regulator can control the relatively large flow and small flow ratio called adjustable ratio R.

When the pressure difference between the two ends of the valve remains constant, the ratio of the larger flow rate to the smaller flow rate is called the ideal adjustable ratio.

In actual use, the pressure difference between the two ends of the valve is changed, then the adjustable ratio is called the actual adjustable ratio.

9, what is the flow coefficient of the regulating valve C, Cv, KV value /p>

The size of the smooth flow ability of the regulating valve is expressed by the flow coefficient.

1) Engineering unit system Cv definition: when the regulator is fully open, the pressure difference before and after the valve is 1kgf/cm2, and the number of cubic meters of water passed by the temperature of 5~40℃ per hour.

2) British system of units C definition: when the regulator is fully open, the pressure difference before and after the valve is 1bf/in2(1 degree 60. F of gallons per minute of water passing through.

3) International system of Units KV: when the regulating valve is fully opened, the pressure difference before and after the valve is 100kPa, and the number of cubic meters of water passed by the temperature of 5~40℃ per hour.

Cv = 1.17 KV

KV = 1.01C

10, the output force of the actuator to satisfy the control valve which several departments of force /p>

1) Overcome the static unbalance force received by the valve core.

2) Provide tight pressure for seat load.

3) Overcome the packing friction.

4) Additional forces required for specific applications or structures (such as bellows, soft seals, etc.).


Post time: Jan-07-2023

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